首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1637563篇
  免费   129393篇
  国内免费   4146篇
耳鼻咽喉   21143篇
儿科学   52492篇
妇产科学   45360篇
基础医学   230095篇
口腔科学   41958篇
临床医学   149639篇
内科学   331173篇
皮肤病学   36616篇
神经病学   138815篇
特种医学   61450篇
外国民族医学   472篇
外科学   244168篇
综合类   36074篇
现状与发展   3篇
一般理论   798篇
预防医学   129889篇
眼科学   37431篇
药学   114034篇
  7篇
中国医学   3652篇
肿瘤学   95833篇
  2021年   15964篇
  2019年   16572篇
  2018年   22153篇
  2017年   16824篇
  2016年   18752篇
  2015年   21195篇
  2014年   30329篇
  2013年   44318篇
  2012年   61467篇
  2011年   64609篇
  2010年   37616篇
  2009年   35423篇
  2008年   58980篇
  2007年   62315篇
  2006年   62607篇
  2005年   60897篇
  2004年   57988篇
  2003年   54871篇
  2002年   52449篇
  2001年   74987篇
  2000年   76124篇
  1999年   63723篇
  1998年   19670篇
  1997年   17689篇
  1996年   17448篇
  1995年   16593篇
  1994年   14969篇
  1993年   13968篇
  1992年   47059篇
  1991年   44565篇
  1990年   42455篇
  1989年   40514篇
  1988年   37149篇
  1987年   36285篇
  1986年   33837篇
  1985年   32210篇
  1984年   24985篇
  1983年   21080篇
  1982年   13464篇
  1981年   11977篇
  1979年   21423篇
  1978年   15298篇
  1977年   12686篇
  1976年   11911篇
  1975年   12089篇
  1974年   14436篇
  1973年   13931篇
  1972年   12982篇
  1971年   11777篇
  1970年   11168篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
Ninety-seven inpatients with tardive dyskinesia (average AIMS score = 13), the majority of whom were schizophrenic, were studied. Forty patients were Caucasian, and 57 were African-American. The APOE genotypes of these patients were compared to previously published genotypes of controls and with previously published studies of APOE genotypes in patients with schizophrenia. There were no significant differences in APOE allele frequencies comparing the African-American tardive dyskinesia population and the African-American control groups. In contrast, significant (< 0.05) P values were obtained comparing the Caucasian tardive dyskinesia population to the Caucasian controls, when comparing allele frequencies and genotypic frequencies. This study suggests that Caucasians bearing an APOE2 allele are at increased risk of developing tardive dyskinesia, whereas African-Americans are not. APOE genotype-specific risks of both tardive dyskinesia and Alzheimer's disease that vary across populations could be due to recruitment of patients or controls or could be due to modifying effects of differing genetic or environmental backgrounds. The mechanism by which the APOE2 allele increases risk of tardive dyskinesia is not known. Further information about the mechanisms of increased risk of tardive dyskinesia could result in stratification of prescribing practices weighing the costs of medications against the relative risk of side effects.  相似文献   
32.
33.
34.
Photodynamic therapy (PDT) is based on the selective light activation of an exogenously given drug to patients. PDT acts mainly on cell membranes either of neovascular endothelial cells or of cancer cells leading to cancer cell death. Six drugs are now marketed based on clinical assays in various indications, which showed a clear cost efficiency as compared to other classical procedures. PDT is easy to handle and can be performed in medical installations fitting the conditions of health care in developing countries. Its cost effectiveness could represent an appropriate solution to the increasing number of cancers of various origin. However despite all the clinical results now available, PDT development remains slow. The reasons for this situation include cost of development, intellectual property, and competition between pharmaceutical companies.  相似文献   
35.
36.
37.
38.
39.
40.
OBJECTIVE: To establish reference intervals for the fetal right, left and total lung volumes and heart volume between 12 and 32 weeks of gestation. METHODS: Fetal lung and heart volumes were measured using three-dimensional (3D) ultrasound in 650 normal singleton pregnancies at 12-32 weeks. The VOCAL (Virtual Organ Computer-aided AnaLysis) technique was used to obtain a sequence of six sections of each lung and the heart around a fixed axis, each after a 30 degrees rotation from the previous one. The rotation axis for the lungs extended from the apex to the upper limit of the diaphragm dome, and the rotation axis for the heart extended from its apex to its connection to the great vessels. The contour of each of these organs was drawn manually in the six different rotation planes to obtain the 3D volume measurement. In 60 cases the fetal lungs and heart volumes were measured by the same sonographer twice and also by a second sonographer once in order to compare the measurements and calculate intra- and interobserver agreement. RESULTS: The total lung volume and heart volume increased with gestation, from respective mean values of 1.6 and 0.6 mL at 12 weeks to 10.9 and 4.3 mL at 20 weeks and 49.3 and 26.6 mL at 32 weeks. The right to left lung volume ratio did not change significantly with gestation (median, 0.7), whereas the heart to total lung volume ratio increased with gestation from about 0.3 at 12 weeks to 0.5 at 32 weeks. In the Bland-Altman plot, the difference between paired measurements by two sonographers was, in 95% of the cases, less than 0.05, 0.5 and 1.9 mL for each lung at 12-13, 19-22 and 29-32 weeks, respectively, and the corresponding values for the heart volumes were 0.04, 0.4 and 2.3 mL. CONCLUSIONS: In normal fetuses the lung and heart volumes increase between 12 and 32 weeks of gestation. The extent to which in pathological pregnancies possible deviations in these measurements from normal prove to be useful in the prediction of outcome remains to be determined.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号